This invention relates in general to microvalves for controlling the flow of fluid through a fluid circuit. In particular, this invention relates to an improved structure for such a microvalve that facilitates more efficient electrical performance, operates at a relatively high overvoltage condition, and has a reduced size and weight relative to a conventional microvalve such that the relative reduction in size and weight facilitates improved manufacturability.
Generally speaking, a micro-electro-mechanical system (MEMS) is a system that not only includes both electrical and mechanical components, but is additionally physically small, typically including features having sizes that are generally in the range of about ten micrometers or smaller. The term “micro-machining” is commonly understood to relate to the production of three-dimensional structures and moving parts of such micro-electro-mechanical system devices. In the past, micro-electro-mechanical systems used modified integrated circuit (e.g., computer chip) fabrication techniques (such as chemical etching) and materials (such as silicon semiconductor material), which were micro-machined to provide these very small electrical and mechanical components. More recently, however, other micro-machining techniques and materials have become available.
As used herein, the term “micro-machined device” means a device including features having sizes that are generally in the range of about ten micrometers or smaller and, thus, is at least partially formed by micro-machining. As also used herein, the term “microvalve” means a valve including features having sizes that are generally in the range of about ten micrometers or smaller and, thus, is also at least partially formed by micro-machining. Lastly, as used herein, the term “microvalve device” means a micro-machined device that includes a microvalve, but further includes additional components. It should be noted that if components other than a microvalve are included in the microvalve device, these other components may be either micro-machined components or standard-sized (i.e., larger) components. Similarly, a micro-machined device may include both micro-machined components and standard-sized components.
A variety of microvalve structures are known in the art for controlling the flow of fluid through a fluid circuit. One well known microvalve structure includes a displaceable member that is supported within a closed internal cavity provided in a valve body for pivoting or other movement between a closed position and an opened position. When disposed in the closed position, the displaceable member substantially blocks a first fluid port that is otherwise in fluid communication with a second fluid port, thereby preventing fluid from flowing between the first and second fluid ports. When disposed in the opened condition, the displaceable member does not substantially block the first fluid port from fluid communication with the second fluid port, thereby permitting fluid to flow between the first and second fluid ports.
End users of this conventional microvalve may require that the microvalve be able to sustain and remain operational at an input voltage increase, or overvoltage, of about 20 percent. Additionally, during assembly of a conventional microvalve, great care must be taken to accurately position the displaceable member within the closed internal cavity provided in the valve body to ensure proper function of the microvalve after assembly. It would be desirable, therefore, to provide a structure for microvalve that can operate at a relatively high overvoltage condition, and in which manufacturability is improved.